Systems are known from the prior art for exhaust gas recirculation of internal combustion engines in motor vehicles. In the systems for exhaust gas recirculation of this kind, the fresh air taken in for the internal combustion engine is mixed with cooled or uncooled exhaust gas in order to meet the legal guidelines of the exhaust gas/emission regulations in regard to nitrogen oxides, but also the emission of hydrocarbons, particles, or carbon dioxide, or to lower the fuel consumption. In this process, exhaust gas is removed from the engine's exhaust gas section and after mixing with fresh air it is returned for combustion once more.
In order to control a mass flow of exhaust gas flowing through the turbocharger, that is, the turbine side of the turbocharger, a bypass valve, also known as a “waste gate” is used, and to control the mass flow of intake air flowing through the turbocharger, that is the compressor side of the turbocharger, a divert-air valve known as a blow-off valve or pop-off valve is used.
For a predetermined charge pressure, the bypass valve configured in particular as a flap valve is opened by means of an actuator arranged on the compressor side of the turbocharger, so that at least a portion of the mass flow of exhaust gas is ducted past the turbine of the turbocharger in order to prevent a rise in the number of revolutions of the turbine. The bypass valve is controlled in this case by a control rod of an electric actuator or by a siphon.
The divert-air valve, which is configured in particular as a seat valve and controlled by a pressure difference or electrically, is used so as not to damage the turbocharger upon sudden drop in the power demand for the engine and thus sudden decrease in the mass air flow through the turbocharger.
Various systems are known from the prior art for exhaust gas recirculation, including both Diesel engine and Otto engine systems, while in each case an exhaust gas recirculation is employed in the high pressure region and/or an exhaust gas recirculation is employed in the low pressure region. Furthermore, for exhaust gas recirculation in the low pressure region one distinguishes between a removal of the exhaust gas upstream and downstream from the exhaust gas aftertreatment, such as a catalyst. A system for exhaust gas recirculation can have an exhaust gas heat exchanger, valves usually designed as seat or poppet valves, and bypass sections with bypass valves usually designed as a flap valve or a poppet valve, electrically or siphon operated.
FIG. 1 shows a system 1′ for air ducting of an internal combustion engine 3 with arrangements 2a′, 2b′ for recirculation of exhaust gas known from the prior art.
The system 1′ has an intake line 8 to draw in combustion air for the internal combustion engine 3. Through the intake line 8, fresh air is drawn in from the surroundings through the compressor side of a turbocharger 5 in the flow direction 9. The compressed air is taken through a charge air cooler 10 to the internal combustion engine 3 and distributed among the individual cylinders.
The exhaust gas produced during the combustion is taken away by the exhaust gas line 4 across the turbine side of the turbocharger 5. The turbine side and the compressor side of the turbocharger 5 are mechanically coupled, for example, by a shaft, so that the turbine drives the compressor and thus increases the air throughput or decreases the suction work of the pistons of the internal combustion engine 3. The turbocharger 5 consequently draws the energy for compression of the intake air from the residual exhaust gas pressure. The exhaust gas is taken in the flow direction 7 of the exhaust gas, after passing through the turbine side of the turbocharger 5 and devices 6a, 6b for aftertreatment of the exhaust gas, to the surroundings.
The exhaust gas line 4 and the intake line 8 are fluidically connected via arrangements 2a′, 2b′ for recirculation of exhaust gas, the first arrangement 2a′ for exhaust gas recirculation operating in the high pressure region and the second arrangements 2b′ for exhaust gas recirculation operating in the low pressure region. The first arrangement 2a′ connects the exhaust gas line 4 in the flow direction 7 of the mass flow of exhaust gas upstream from the turbine side of the turbocharger 5 to the intake line 8 in the flow direction 9 of the intake mass air flow downstream from the charge air cooler 10 and thus downstream from the compressor side of the turbocharger 5. The second arrangements 2b′ connect the exhaust gas line 4 in the flow direction 7 of the mass flow of exhaust gas downstream from the turbine side of the turbocharger 5 to the intake line 8 in the flow direction 9 of the intake mass air flow upstream from the compressor side of the turbocharger 5.
In each case the arrangements 2a′, 2b′ are configured by an exhaust gas heat exchanger 11a′, 11b′ for exhaust gas cooling and a valve 14a′, 14b′ for regulating the quantity and thus the dosage of the recirculated mass flow of exhaust gas.
One of the arrangements 2b′ for recirculation of exhaust gas in the low pressure region furthermore enables a recirculation of clean exhaust gas, since the exhaust gas is removed in the flow direction 7 downstream from a device 6a for aftertreatment of the exhaust gas.
In the systems known to the prior art for exhaust gas recirculation of an internal combustion engine 3 in a motor vehicle one uses for both the exhaust gas recirculation in the high pressure region and for exhaust gas recirculation in the low pressure region exhaust gas heat exchangers 11a′, 11b′ and valves 14a′, 14b′ with actuators as well as bypasses 12a′, 12b′ with bypass valves 13a′, 13b′ with actuators. Furthermore, the turbochargers 5 of the traditional systems of exhaust gas recirculation have a “waste gate” valve and a divert-air valve, each with actuators.
Thus, the known systems designed for the six different application options—exhaust gas recirculation in the high pressure region, exhaust gas recirculation in the low pressure region, each time with bypasses as well as turbocharger with “waste gate” valve and divert-air valve—are configured with at least ten different components, that is, each time in addition with the exhaust gas heat exchangers and the bypass valves. The separate configuration of the components results in an increased number of parts, an increased space requirement, a high weight, and increased manufacturing costs and installation costs. Six of the ten components are valves, which are optionally electrically actuated.